Embodiments disclosed herein relate to ink compositions. More particularly, embodiments disclosed herein relate to amorphous ureas used in phase change inks comprising mixtures of amorphous and crystalline components.
Phase change inks are desirable for ink jet printers because they remain in a solid phase at room temperature facilitating shipping, long term storage, and the like. In addition, the problems associated with nozzle clogging as a result of ink evaporation with conventional liquid ink jet inks are largely eliminated, thereby improving the reliability of the ink jet printing. Further, in phase change ink jet printers the ink droplets are applied directly onto the final recording medium, while the droplets solidify almost immediately upon contact so that migration of ink along the printing medium is prevented and dot quality is improved.
Numerous phase change inks may employ a mixture of crystalline and amorphous components. The crystalline material may impart a hardness and rapid phase change. The amorphous material, typically a viscous, tacky material, may aid in adhesion to the substrate and may help plasticize the crystalline component to prevent embrittlement and cracking of the printed image. Many amorphous materials that have been employed as the amorphous component of phase change inks comprise ester functional groups. However, esters are prone to hydrolysis which may compromise the properties of the formulated phase change ink. Other issues of current phase change inks that may arise in currently employed amorphous components include lack of thermal stability and/or insufficient ability to confer rub resistance to the printed image.